Thiopyran derivative, polymer, resist composition, and method for manufacturing semiconductor device using such resist composition

ABSTRACT

To provide a thiopyran derivative, having a structure expressed by the following general formula 1: where X is O or S; R1 is —H, —CH3, C2-4 alkyl group, thioether group, or ketone group; R2 is —H, —CH3, or trifluoromethyl group; and R1 and R2 may be identical to or different from each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT/JP2007/074128, filed on Dec.14, 2007, the entire contents of which are incorporated herein byreference.

FIELD

The present invention relates to a novel thiopyran derivative, polymercontaining the thiopyran as a monomer unit, a resist compositioncontaining such the polymer, and a method for manufacturing asemiconductor device using such the resist composition.

BACKGROUND

In the current technology of the semiconductor integrated circuit,higher integration has been achieved and as a result, the minimumpattern size reaches the region of 100 nm or less. For the formation offine patterns, exposure technique is regarded as very important, and theexposure technique enables to attain a desired pattern in the followingmanner. At first, a resist film is applied onto a substrate to beprocessed (surface to be processed) to which a thin film has beenformed, the resist film is selectively exposed with light and thendeveloped so as to form a pattern, a dry etching is performed using thethus obtained pattern as a mask, and finally the resist pattern isremoved to obtain the desired pattern.

In order to realize downsizing of the pattern, it is effective toimprove and develop both an exposure light source using the shortenwavelength and a resist material of high resolution corresponding to thecharacteristics of the exposure light source. Currently, ArF excimerlaser exposure tools have been on the market. However, these exposuretools themselves are quite expensive and a large scale of cost isexpected at the time the exposure tool is updated for the purpose ofshortening the wavelength of the exposure tool. Moreover, it is not easyto develop a resist material which corresponds to the shorten wavelengthof exposure light, and it is extremely difficult to realize thedownsizing of the pattern by only shortening the wavelength of theexposure device.

For these reasons, much attention has been attracted to a new exposuretechnique, a liquid immersion lithography, in the art. In this method,the space between the projection lens and wafer in the exposure deviceis filled with liquid having a lager refractive index n than that of airso as to improve and obtain higher resolution than that of the relatedart.

The resolution of the exposure device is determined by using thefollowing Calculation Formula 1:Resolution R=Coefficient k×Wavelength λ of light source/Numericalaperture NA  Calculation Formula 1

As represented with Calculation Formula 1, the resolution R improves (besmaller), as the wavelength λ of an exposure light source is shorter andthe numerical aperture NA is larger. Note that, the numerical apertureof the projection lens is represented as: NA=n×sin α, where n isrefractive index of a medium through which the exposure light istransmitted, and α is an angle formed between the exposure light and alight axis of the projection lens. Since the exposure of light isgenerally performed in atmospheric air, the refractive index n is 1(i.e., n=1). The liquid immersion exposure method applies the exposuresystem in which the space between the projection lens and the wafer isfilled with a liquid having the refractive index n larger than 1 (i.e.,n>1). Accordingly, the refractive index is enlarged from 1 to n (anumber larger than 1) in the relative formula of the numerical apertureNA: NA=n×sin α. At the incident angle α of the same exposure light, theresolution R (minimum resolution size) will be reduced in 1/n as NA isenlarged n time(s). In addition, there is also the advantage such that,in the case where the value of NA is set the same, the depth of focus isdeepened n times as a can be reduced by enlarging n.

In accordance with the conventional exposure in the air, the numericalaperture NA cannot be adjusted to 1 or larger, as a refractive index ofthe air between the resist and the lens becomes the factor to limit thenumerical aperture NA. However, in accordance with liquid immersionlithography using water, the refractive index relative to the lighthaving a wavelength of 193 nm is increased to 1.44. Therefore, it hasbeen said that the numerical aperture NA can be increased up to about1.4 on theory. However, as the numerical aperture NA is increased, theangle of the light incident to the resist film is significantlyincreased. Therefore, the depth of focus (a margin of the focal distancecapable of resolution) is reduced. Moreover, to attain higher resolution(the smaller value of the resolution R), liquid immersion lithography ofthe next generation, which uses a medium having the higher refractiveindex (n>1.6) than that of water, has been studied. In the case of thisliquid immersion lithography of the next generation, it is theoreticallypossible to increase the numerical aperture NA by about 1.6 times forthe exposure in the air, but the current material for an ArF resist hasthe insufficient refractive index (the refractive index n is about 1.7to the light having a wavelength of 193 nm). Therefore, the totalreflection occurs on the surface of the resist film so that the lightdoes not reach to the inner part of the resist film. As a result, animage cannot be formed, and hence a pattern cannot be formed.

To solve these problem, the studies have been conducted to increase arefractive index of a resist material. However, not so many materials,which can effectively increase a refractive index with maintainingtransparency at 193 nm, without impairing acid reactivity desirable forforming a pattern, have not been known in the art. As a familiar exampleof the material whose refractive index is increased, a resin lens usedfor glasses and the like has been known. For such material, it is commonthat the refractive index of the material is increased by introducingheavy metals, aromatic rings, heavy halogen atoms such as bromine andiodine, or sulfur atoms into the material. In the case of the ArF resistmaterial, however, there is a limitation in the method for introducingsulfur atoms because of the transparency at 193 nm, or the problem ofcontamination.

As prior examples of the resist material whose refractive index isincreased, those using a resin containing sulfur, which has a problem inthe transparency thereof, disclosed in Idriss Blakey et al., Proc. SPIE,6519, 651909 (2007), an alicyclic material disclosed in Japanese PatentApplication Laid-Open (JP-A) No. 2006-89412, and a curable compositioncontaining aromatic heterocyclic (meth)acrylate disclosed in JP-A No.2005-133071 have been known. Therefore, it has been desired to develop amaterial whose refractive index is increased, and which can be easilyproduced.

SUMMARY

The present invention aims at solving the problems present in the art,and achieving the following objects.

Accordingly, it is an object in one aspect of the invention to provide:a thiopyran derivative useful for increasing a refractive index of aresin for a resist composition without impairing transparency or acidsensitivity of the resist composition; a polymer containing thethiopyran derivative as a monomer unit; a resist composition containingthe polymer; and a method for manufacturing a semiconductor device usingthe resist composition.

According to an aspect of the invention, a thiopyran derivative has astructure expressed by the following general formula 1:

In the general formula 1, X is O or S; R₁ is —H, —CH₃, C₂₋₄ alkyl group,thioether group, or ketone group; R₂ is —H, —CH₃, or trifluoromethylgroup; and R₁ and R₂ may be identical to or different from each other.

According to another aspect of the invention, a polymer contains amonomer unit containing the thiopyran derivative.

According to another aspect of the invention, the resist compositioncontains the polymer.

According to another aspect of the invention, the method formanufacturing a semiconductor device contains: forming a resist filmformed of the resist composition on a processing surface; exposing theresist film to light; and developing the resist film so as to patternthe resist film.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram explaining one example of a method formanufacturing a semiconductor device of the invention, and illustrates astate where an interlayer insulating film is formed on a siliconsubstrate.

FIG. 2 is a schematic diagram explaining one example of a method formanufacturing a semiconductor device of the invention, and illustrates astate where a titanium film is formed on the interlayer insulating filmof FIG. 1.

FIG. 3 is a schematic diagram explaining one example of a method formanufacturing a semiconductor device of the invention, and illustrates astate where a resist film is formed on the titanium film, and a holepattern is formed in the titanium film.

FIG. 4 is a schematic diagram explaining one example of a method formanufacturing a semiconductor device of the invention, and illustrates astate where the hole pattern is also formed in the interlayer insulatingfilm.

FIG. 5 is a schematic diagram explaining one example of a method formanufacturing a semiconductor device of the invention, and illustrates astate where a Cu film is formed on the interlayer insulating film towhich the hole pattern has been formed.

FIG. 6 is a schematic diagram explaining one example of a method formanufacturing a semiconductor device of the invention, and illustrates astate where the Cu deposited on the interlayer insulating film otherthan on the hole pattern is removed.

FIG. 7 is a schematic diagram explaining one example of a method formanufacturing a semiconductor device of the invention, and illustrates astate where an interlayer insulating film is formed on the Cu plugformed in the hole pattern and on the TiN film.

FIG. 8 is a schematic diagram explaining one example of a method formanufacturing a semiconductor device of the invention, and illustrates astate where a hole pattern is formed in the interlayer insulating layeras the surface layer, and a Cu plug is formed therein.

FIG. 9 is a schematic diagram explaining one example of a method formanufacturing a semiconductor device of the invention, and illustrates astate where a three-layered wiring is formed.

DESCRIPTION OF EMBODIMENTS Thiopyran Derivative

The thiopyran derivative contains a structure expressed by the followinggeneral formula 1:

In the general formula 1, X is O or S; R₁ is —H, —CH₃, C₂₋₄ alkyl group,thioether group, or ketone group; R₂ is —H, —CH₃, or trifluoromethylgroup; and R₁ and R₂ may be identical to or different from each other.

Since a sulfur element is contained in the thiopyran derivative, when apolymer containing this thiopyran derivative as a monomer unit (aconstitutional unit) is used in a resist composition, a refractive indexof the resin for the resist composition is increased without impairingthe properties of the resist composition, such as transparency and acidsensitivity, and the resist composition can be applicable to the liquidimmersion lithography of the next generation, which attempts to form adown-sized pattern using a lens of a large aperture (a lens having alarge numerical aperture, NA).

The thiopyran derivative and the production method thereof will beexplained hereinafter.

In General Formula 1, C3-4 alkyl group of R₁ may be of straight chain orbranched chain, and preferable examples thereof include various propylgroups and butyl groups. Moreover, a thioester structure in which X is Sis preferable for the purpose of increasing the refractive index, andsuch the structure is desirable.

Examples of the thiopyran derivative include the following compounds:

<Method for Manufacturing Thiopyran Derivative>

These thiopyran derivatives can be synthesized in accordance with theconventional methods, and as described in Idriss Blakey et al., Proc.SPIE, 6519, 651909 (2007), the thiopyran derivative can be generallyobtained by an esterification reaction between acid chloride and analcohol compound or a thiol compound. Specifically, for example, thesame mole amounts of an alcohol or thiol compound and a base catalystsuch as triethyl amine are added to a solvent such as dried methylenechloride, and the mixture is cooled down to 0° C. to −20° C. Thereafter,for example, acrylchloride was dropped thereto through a droppingfunnel, triethyl amine salt is removed after loss of the raw material isconformed by a thin film chromatography or gas chromatography, and thenpurification is performed for example, by column chromatography toeasily form a desired compound.

(Polymer)

Next, the polymer (the resin for a positive resist composition)containing the thiopyran derivative as a monomer unit will be explained.

The polymer is suitably selected depending on the intended purposewithout any restriction, provided that it contains the thiopyranderivative as a monomer unit. For example, the thiopyran derivative maybe copolymerized with other monomer units.

Since the polymer contains the monomer unit containing the thiopyranderivative, when a polymer containing this thiopyran derivative as amonomer unit is used in a resist composition, a refractive index of theresin for the resist composition is increased without impairing theproperties of the resist composition, such as transparency and acidsensitivity, and the resist composition can be applicable to the liquidimmersion lithography of the next generation, which attempts to form adown-sized pattern using a lens of a large aperture (a lens having alarge numerical aperture, NA).

<Amount of Monomer unit Containing Thiopyran Derivative in Polymer>

It is desirable that the amount of the monomer unit containing thethiopyran derivative in the polymer (the resin for a positive resistcomposition) be determined carefully considering the predeterminedrefractive index, resulting properties of a resist composition, such assensitivity, resolution and etching resistance. The amount of themonomer unit containing the thiopyran derivative is preferably in therange of 0.1 mol % to 70 mol %, more preferably 10 mol % to 55 mol %.When the amount of the thiopyran derivative in the polymer is less than10 mol %, the refractive index of the resulted resin for a resistcomposition cannot be increased. When the amount of the thiopyranderivative in the polymer is more than 55 mol %, an effect originatedfrom other monomer units to be copolymerized (for example, high opticaltransparency and high etching resistance originated from adamanthylgroup, or high adhesion originated from lactone group) cannot beattained, and absorption of ultraviolet rays is increased, reducing thetransmittance of the light having a wavelength of 193 nm.

<Other Monomer units>

The other monomer units can be suitably selected depending on theintended purpose without any restriction, but those monomer units havingacid labile groups (e.g. monomer units having alicyclic groups thatreacts with acid) are preferable. The resin for positive resistcomposition itself is generally alkali-insoluble, but the resin becomesalkali-soluble after the acid labile groups are reacted.

<<Acid Reactive Group>>

The acid reactive group is suitably selected depending on the intendedpurpose without any restriction. Preferably examples thereof include:tertially ester such as t-butyl group; acetal group such as ethoxyethyl,3-oxocyclohexyl group, 2-alkyl-2-adamanthyl group,1-alkyl-1-cyclopenthyl group, 1-alkyl-1-cyclohexyl group,2-adamanthyloxymethyl group, 1-methyladamanthyloxymethyl group, and thelike. Among them, the acid labile group having an alicyclic structuresuch as 2-alkyl-2-adamanthyl group, 2-adamanthyloxymethyl group, or1-methyl adamanthyloxymethyl group is more preferable since such acidlabile group provides etching resistance and transparency at thewavelength of 193 nm.

Moreover, the polymer preferably further contains a monomer unitincluding a lactone derivative (e.g., a monomer unit containing alactone group that will be a side chain in a polymer). As a lactone ringis highly polar, the property contributes adhesion properties of aresist pattern, and it also imparts a suitable alkali-solubility at theexposed area due to its slight alkali-solubility.

<<Lactone Derivatives>>

A lactone derivative is suitably selected depending on the intendedpurpose without any restriction. Preferable examples thereof includeγ-butyrolactone group, δ-lactone group, alicyclic lactone combined withnorbornane or cyclohexane ring. The alicyclic lactone is particularlypreferable since it contributes an etching resistance of the resultedresist composition.

In the case where the polymer (the resin) contains the monomer unitcontaining the thiopyran derivative, the monomer unit containing theacid labile group, and the monomer unit containing a lactone derivative,the ratio of these units is arbitral, but it is desirable that the ratiois adjusted considering the balance between resolution, etchingresistance and refractive index.

Moreover, the polymer (the resin for positive resist) containing themonomer unit containing the thiopyran derivative may further containmonomer unit having other functions than mentioned above. Examples ofsuch the unit include a unit containing an alkali-soluble group such ascarboxyl group or hexafluorocarbinol group at a site which will be aside chain in the resulted polymer, a unit containing a hydroxyl groupsuch as 2-hydroxyethyl group or 3-hydroxyadamanthyl group, and the like.The amount of these units in the polymer should be carefully determinedfor desired properties such as adhesion of the resist film to asubstrate, alkali-dissolution rate of the exposed area, and the like.

(Resist Composition)

The resist composition is suitably selected depending on the intendedpurpose without any restriction, provided that it contains theaforementioned polymer. In the case of the positive resist composition,the resist composition contains an acid-generating agent together withthe polymer (the resin).

A solvent used for the positive resist composition is suitably selectedwithout any restriction, provided that it is commonly used for resistcompositions, but is preferably selected considering solubility andcoating performance of the polymer (the resin), the acid-generatingagent, and other additives.

Moreover, the resist composition may further contain a quencher. Byadding a quencher to the resist composition, the exposure contrast canbe improved.

The resist composition may further contain a surfactant. A surfactant isadded to the resist composition mainly for improving the coatingperformance thereof.

Moreover, the thiopyran derivative or homopolymer of the thiopyranderivative can be added to the positive resist composition as anadditive, and such use of the thiopyran derivative or homopolymer ispreferable. In the case where monomers of the thiopyran derivative areadded as they are, it is desirable that the composition be prepared sothat the monomers does not leach into a medium for liquid immersion.There is no problem in the addition of the monomers when the monomerswill not leach. However, when the leaching of the monomers is concerned,it is preferred that, for example, a small amount (e.g., 0.5 parts bymass with respect to 100 parts by mass of the base resin) of afluororesin or silicone resin, which easily causes a phase separation toan acrylic resin, be added to form a film which prevents the additivesubstances from leaching. The amount of the monomers can beappropriately adjusted depending on the desirable refractive index andpatterning properties, but is preferably 50 parts by mass or less withrespect to 100 parts by mass of the base resin.

In the case where homopolymer of the thiopyran derivative is added, anyconsideration is not particularly required as long as a resist film of adesirable quality can be formed, as the elution to the liquid immersionmedium will not be a problem compared to the case of the monomer, butgenerally a phase separation tends to occur more easily. The amount ofthe homopolymer can be appropriately adjusted depending on the desirablerefractive index and patterning properties, but is preferably 100 partsby mass or less with respect to 100 parts by mass of the base resin.

<Acid-generating Agent>

The acid-generating agent is suitably selected from those known in theart without any restriction. Preferable examples thereof includecommonly used trifluoromethanesulfonium salt, perfluorobutanesulfoniumsalt, perfluorodisulfoneimide salt, and the like. The amount thereof ispreferably in the approximate range of 0.1 parts by mass to 10 parts bymass with respect to 100 parts by mass of the resin, though it will beadjusted depending on the balance with the sensitivity or resolution.

<Solvent>

The solvent is suitably selected depending on the intended purposewithout any restriction. Preferable examples of such solvent includepropylene glycol monomethylether acetate, 2-heptanone, ethyl lactate,and cyclohexanone. Optionally, an auxiliary solvent can also be used. Asan auxiliary solvent, propylene glycol monomethyl ether orγ-butyrolactone is used preferably, and especially an organic solventhaving a boiling point of about 100° C. to about 200° C. and excellentsolubility of the resin is used preferably. A use of such the organicsolvent is preferable, as it is suitably used for coating, and the rapiddrying is prevented at the coating process.

<Quencher>

The quencher is suitably selected depending on the intended purposewithout any restriction. Preferable examples thereof includenitrogen-containing compounds such as tri-n-octyl amine,2-methylimidazole, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU),1,5-diazabicyclo[4.3.0]non-5-ene (DBN), diphenyl amine, triethanolamine, and the like.

<Surfactant>

The surfactant is suitably selected depending on the intended purposewithout any restriction. Preferable examples thereof include nonionicsurfactants free from metal ion such as sodium salt or potassium salt.Particularly preferable examples includepolyoxyethylene-polyoxypropylene condensed derivatives, polyoxyalkylenealkyl ether, polyoxyethylene alkyl ether, polyoxyethylene derivative,sorbitane fatty acid ester, glycerin fatty acid ester, primary alcoholethoxylate, phenol ethoxylate, silicone surfactant, andfluorosurfactant. Moreover, the surfactant may be selected from ionicsurfactants other than the ones mentioned above, provided that the ionicsurfactants are of metal salt-free. It is assumed that the same effectcan be attained even if the aforementioned nonionic surfactant isreplaced with such the metal salt-free ionic surfactant.

Since the resist composition contains the polymer, a refractive index ofthe resist base resin is increased without impairing the properties ofthe resist composition, such as transparency and acid sensitivity, andthe resist composition can be applicable to the liquid immersionlithography of the next generation, which attempts to form a down-sizedpattern using a lens of a large aperture (a lens having a largenumerical aperture NA).

(Method for Manufacturing Semiconductor Device)

The method for manufacturing a semiconductor device at least contains aresist film forming step, an exposing step, and a developing step,preferably further contains a heating step, and may further containsuitably selected other steps, if necessary. It is preferred that theheating step be performed after the exposing step.

In the method for manufacturing a semiconductor device, a resist filmformed of the resist composition is formed on a processing surface,followed by exposing the resist film to light. The resist film is thendeveloped to form the patterned resist film.

<Resist Film Forming Step>

The resist film forming step is forming a resist film formed of theresist composition on a processing surface.

The resist film can be formed by a method known in the art, such as bycoating. The coating method is suitably selected from the conventionalcoating methods depending on the intended purpose without anyrestriction. Preferable examples thereof include spin coating. In thecase of the spin coating, as preferred conditions thereof, the rotationnumber is about 100 rpm to about 10,000 rpm, preferably 800 rpm to 5,000rpm, and the duration is about 1 second to about 10 minutes, preferably1 second to 90 seconds.

The thickness of the coating is suitably selected depending on theintended purpose without any restriction.

It is preferred that the coated resist composition be pre-baked (heatedand dried) during or after coating. The conditions and method of thepre-baking are suitably selected depending on the intended purposewithout any restriction, provided that the pre-backing will not softenthe resist film. For example, the temperature of the pre-baking ispreferably about 40° C. to about 150° C., more preferably 80° C. to 120°C., and the duration thereof is preferably about 10 seconds to about 5minutes, more preferably 30 seconds to 90 seconds.

The processing surface is suitably selected depending on the intendedpurpose without any restriction. In the case where the resist film isformed in an electronic device such as a semiconductor, examples of theprocessing surface include surface layers of various members of thesemiconductor device, preferably a substrate such as a silicon wafer anda surface thereof, and a low dielectric film such as various oxide filmsand a surface thereof.

The low dielectric film is suitably selected depending on the intendedpurpose without any restriction, and is preferably a film having adielectric constant of 2.7 or less. Preferable examples of such the lowdielectric film include a porous silica film, and a fluororesin film.

The porous silica film can be formed, for example, by applying amaterial for forming a silica film, subjecting the applied material to aheat treatment so as to remove the solvent, and baking the appliedmaterial.

In the case where the fluororesin film is a fluorocarbon film, thefluororesin film can be formed, for example, by accumulating inaccordance with a RFCVD method (power: 400 W) using a mixed gas of C₄F₈and C₂H₂ or C₄F₈ gas as a source.

<Exposing Step>

The exposing step is selectively exposing the resist film to light.

The exposure can be suitably performed by means of the exposure deviceknown in the art, and is carried out by applying light to the resistfilm. As a result of the application of the light, the photoacid-generating agent contained in the exposed area of the resistcomposition is decomposed to generate acid, causing a curing reaction ofthe resist composition to form a latent pattern.

The light is applied to a partial area of the resist film. The polarityof the resist film is increased as a result of that side chains of theresin are detached by the acid reaction in the partial area due to theapplication of the light, so that the highly polarized partial area isremoved in the developing step described later to form a resist pattern.

In the exposing step, the application of light is carried out inaccordance with liquid immersion lithography. Here, a medium for use inthe liquid immersion lithography may be water, but is preferably liquidhaving a higher refractive index than that of water relative to lighthaving a wavelength of 193 nm.

The exposure light is suitably selected depending on the intendedpurpose without any restriction. Preferably examples thereof includeactivation energy radiation such as ultraviolet ray, X-ray, electronray, excimer laser beam, EUV light, and focused ion beam.

In the case where the ultraviolet ray is used, the ultraviolet rayhaving a wavelength of 200 nm or less is more preferable.

In the case where the excimer laser beam is used, KrF excimer laserlight (wavelength of 248 nm), ArF excimer laser light (wavelength of 193nm), F₂ excimer laser light (wavelength of 157 nm), or the like ispreferable.

<Heating Step>

The heating step is subjecting the exposed resist film to a heatingtreatment (a post-exposure bake, PEB).

As a result of the heating, the elimination reaction of the side chainof the resist resin in the exposed area is accelerated.

The heating temperature is preferably 50° C. to 200° C., more preferably70° C. to 180° C. When the temperature is less than 50° C., theelimination reaction of the side chain of the resin may not beprogressed. When the temperature is more than 200° C., the resistcomposition, which forms the resist film, may be thermally decomposed.

<Development Step>

The development step is removing the exposed area of the resist film todevelop the resist film, after exposing the resist film in the exposingstep and reacting the exposed area of the resist film, so as to form apattern of the resist film (a resist pattern).

The method for removing the reacted area is suitably selected dependingon the intended purpose without any restriction, and examples thereofinclude a method for removing the reacted area using a developer.

The developer is suitably selected depending on the intended purposewithout any restriction, and is preferably an alkali solution. Specificexamples of the alkali solution include a tetramethylammoniumhydroxide(TMAH) solution, and a choline solution, which are commonly used in theproduction of a semiconductor device.

As a result of the developing, the area of the resist film where thelight is applied is dissolved and removed to form (develop) a resistpattern.

<Other Steps>

Other steps are suitably selected depending on the intended purposewithout any restriction. Examples thereof include a patterning step.

<<Patterning Step>>

The patterning step is etching the processing surface using the patternof the resist film (the resist pattern) as a mask so as to pattern theprocessing surface.

The method for the etching is suitably selected from the methods knownin the art depending on the intended purpose without any restriction.Preferable examples thereof include dry etching. The conditions of theetching are suitably selected depending on the intended purpose withoutany restriction.

The method for manufacturing a semiconductor device is suitable for theformation of various resist patterns, such as a line-space pattern, ahole pattern (for a contact hole), a pillar pattern, a trench pattern,and a line pattern, and the resist pattern formed by the method formanufacturing a semiconductor can be used, for example, as a maskpattern, and a reticle pattern, and are suitably used for the productionof functional parts such as metal plugs, various wirings, magneticheads, liquid crystal displays (LCD), plasma display panels (PDP), and asurface acoustic wave (SAW) filter, optical parts used for connection ofoptical wirings, minute parts such as microactuator, and a semiconductordevice.

Specifically, by selectively depositing or etching using as a maskpattern, the resist pattern formed by the method for manufacturing asemiconductor device, a device having a fine processing pattern having aconstant line width and formed of a metal or other materials can bemanufactured, and for example, a semiconductor device having a finewiring having a line width of 100 nm or less can be manufactured.

Moreover, in accordance with the method for manufacturing asemiconductor device, a fine and precise resist pattern can beaccurately formed without causing the defects in the shape, and a higherperformance semiconductor device having a fine wiring pattern, such as aflash memory, DRAM, and FRAM, can be efficiently mass-produced by usingthe resist pattern.

In accordance with the invention, there are provided a thiopyranderivative useful for increasing a refractive index of a resin for aresist composition without impairing properties of the resistcomposition such as transparency and acid sensitivity, a polymercontaining a monomer unit containing the thiopyran derivative, a resistcomposition containing the polymer, and a method for manufacturing asemiconductor device using the resist composition.

Moreover, in accordance with the present invention, there can beprovided: a thiopyran derivative, a polymer, and a resist composition,which are capable of forming a highly precise pattern by high refractiveliquid immersion ArF excimer laser lithography that enables to draw thefiner pattern, and thus largely contributes to the mass-production ofdevices; and a method for manufacturing a semiconductor device using theresist composition.

EXAMPLES

Examples of the invention will be explained hereinafter, but theseexamples shall not be construed as to limit the scope of the invention.

Synthesis Example 1 Synthesis of tetrahydro-2H-thiopyran-4-ylmethacrylate (Thiopyran Derivative of the Following Formula 2)

To a 200-mL three-necked flask fitted with a stirrer bar coated withTeflon™, were added 5.37 g of 4-hydroxytetrahydrothiopyran (manufacturedby SANKYO KASEI Co., Ltd.), 5.08 g of triethyl amine, and 50 mL of driedmethylene chloride, and the mixture was stirred under nitrogenatmosphere at 0° C. To the mixture, 5.0 g of methacryloyl chloride wasslowly added through a dropping funnel, and the resulted mixture wasreacted at 0° C. for 40 minutes, allowed to warm to room temperature,and was further reacted for another 5 hours. After confirming loss ofthe starting material by a thin layer chromatography (TLC), the reactionsolution was poured into a 300-mL separatory funnel, washed with 100 mLof water followed by 100 mL of saturated NaCl solution (brine), anddried with anhydrous sodium sulfate. From the obtained solution, thesolvent was removed by an evaporator, to obtain an oily crude product.The crude product was purified by silica gel chromatography using amixed solution of n-hexane and ethyl acetate to give 5.18 g oftetrahydro-2H-thiopyran-4-yl methacrylate (thiopyran derivative of thefollowing formula 2) (yield: 61.3%).

(1) ¹H-NMR (500 MHz, CDCl₃, internal standard TMS, 6 in ppm): 1.95 (s,3H), 1.9-2.1 (m, 4H), 2.58-2.81 (m, 4H), 4.93 (m, 1H), 5.57 (m, 1H),6.12 (m, 1H)

(2) IR (KBr, cm⁻¹): 2920, 1716, 1635, 1292, 1163, 1018, 814

(3) Refractive index nD=1.506

Synthesis Example 2 Synthesis of 4-methyl-tetrahydro-2H-thiopyran-4-ylmethacrylate (Thiopyran Derivative of the Following Formula 3)

To a 200-mL three-necked flask fitted with a stirrer bar coated withTeflon™, were added 5.95 g of 4-hydroxy-4-methyltetrahydrothiopyran(manufactured by SANKYO KASEI Co., Ltd.), 5.08 g of triethyl amine, and50 mL of dried methylene chloride, and the mixture was stirred undernitrogen atmosphere at 0° C. To the mixture, 5.0 g of methacryloylchloride was slowly added through a dropping funnel, and the resultedmixture was reacted at 0° C. for 30 minutes, allowed to warm to roomtemperature, and was further reacted for another 5 hours. Afterconfirming loss of the starting material by TLC, the reaction solutionwas poured in a 300-mL separatory funnel, washed with 100 mL of waterfollowed by with 100 mL of saturated NaCl solution (brine), and driedwith anhydrous sodium sulfate. From the obtained solution, the solventwas removed by an evaporator, to obtain an oily crude product. The crudeproduct was purified by silica gel chromatography using a mixed solutionof n-hexane and ethyl acetate to give 5.89 g of4-methyl-tetrahydro-2H-thiopyran-4-yl methacrylate (thiopyran derivativeof the following formula 3) (yield: 59.4%).

(1) ¹H-NMR (500 MHz, CDCl₃, internal standard TMS, 6 in ppm): 1.53 (s,3H), 1.72 (m, 2H), 1.93 (d, 3H), 2.41-2.60 (m, 4H), 2.84-2.90 (m, 4H),5.53 (q, 1H), 6.05 (d, 1H)

(2) IR (KBr, cm⁻¹): 2920, 1713, 1636, 1300, 1165, 1082, 920

(3) Refractive index nD=1.507

Synthesis Example 3 Synthesis of polytetrahydro-2H-thiopyran-4-ylmethacrylate (Polymer of the Following Formula 4)

To a 100-mL eggplant-shaped flask fitted with a stirrer car coated withTeflon™, were added 1.39 g of tetrahydro-2H-tiopyran-4-yl methacrylate,and 5 mL of dioxane. The mixture was then stirred, and nitrogen gas wasbubbled for 15 minutes to remove oxygen in the reaction atmosphere. Tothis, was added 0.37 g of AIBN as a radical polymerization initiator,and the flask was placed in an oil bath at 70° C. for 5 hours. Theobtained reaction mixture was cooled to room temperature, and dilutedwith dioxane to be about 7 mL in volume. The solution was dropped into250 mL of methanol with stirring to give white precipitate. Afterfiltering with a glass filter, the obtained precipitated resin was driedin vacuo at 50° C. for 6 hours. The resulted resin was dissolved inabout 7 mL of THF, was again precipitated in 250 mL of methanol, andfiltered and dried in the aforementioned manner to providepolytetrahydro-2H-thiopyran-4-yl methacrylate (polymer of the followingformula 4). The yield was 0.9 g, the weight average molecular weight was12,800 (standard polystylene equivalent), and polydispersion (Mw/Mn) was1.88. Note that the molecular weight was measured by GPC (HLC-8220 GPC,manufactured by Tosoh Corporation).

(1) IR (KBr disk, cm⁻¹): 2947, 1724, 1429, 1269, 1149, 999, 871

Synthesis Example 4) Synthesis of poly4-methyl-tetrahydro-2H-thiopyran-4-yl methacrylate (Polymer of theFollowing Formula 5)

To a 100-mL eggplant-shaped flask fitted with a stirrer car coated withTeflon™, were added 1.3 g of 4-methyl-tetrahydro-2H-tiopyran-4-ylmethacrylate, and 4 mL of dioxane. The mixture was then stirred, andnitrogen gas was bubbled for 15 minutes to remove oxygen in the reactionatmosphere. To this, was added 0.29 g of AIBN as a radicalpolymerization initiator, and the flask was placed in an oil bath at 70°C. for 4.5 hours. The obtained reaction mixture was cooled to roomtemperature, and diluted with dioxane to be about 10 mL in volume. Thesolution was dropped into 250 mL of methanol with stirring to give whiteprecipitate. After filtering with a glass filter, the obtainedprecipitated resin was dried in vacuo at 50° C. for 6 hours. Theresulted resin was dissolved in about 10 mL of THF, was againprecipitated in 250 mL of methanol, and filtered and dried in theaforementioned manner to provide poly4-methyl-tetrahydro-2H-thiopyran-4-yl methacrylate (polymer of thefollowing formula 5). The yield was 0.75 g, the weight average molecularweight was 7,560 (standard polystylene equivalent), and polydispersion(Mw/Mn) was 1.48. Note that the molecular weight was measured by GPC(HLC-8220 GPC, manufactured by Tosoh Corporation).

(1) IR (KBr disk, cm⁻¹): 2920, 1713, 1636, 1300, 1165, 1082, 920

Synthesis Example 5) Synthesis of poly(2-methyl-2-adamanthylmethacrylate-tetrahydro-2H-thiopyran-4-yl methacrylate)(Polymer of theFollowing Formula 6)

To a 100-mL eggplant-shaped flask fitted with a stirrer car coated withTeflon™, were added 1.31 g of 2-methyl-adamanthyl methacrylate, 1.0 g oftetrahydro-2H-tiopyran-4-yl methacrylate, and 3.6 mL of dioxane. Themixture was then stirred, and nitrogen gas was bubbled for 15 minutes toremove oxygen in the reaction atmosphere. To this, was added 0.27 g ofAIBN as a radical polymerization initiator, and the flask was placed inan oil bath at 70° C. for 5 hours. The obtained reaction mixture wascooled to room temperature, and diluted with dioxane to be about 20 mLin volume. The solution was dropped into 500 mL of methanol withstirring to give white precipitate. After filtering with a glass filter,the obtained precipitated resin was dried in vacuo at 50° C. for 6hours. The resulted resin was dissolved in about 20 mL of THF, was againprecipitated in 500 mL of methanol, and filtered and dried in theaforementioned manner to provide poly(2-methyl-2-adamanthylmethacrylate-tetrahydro-2H-thiopyran-4-yl methacrylate) (polymer of thefollowing formula 6). The yield was 1.91 g, the weight average molecularweight was 18,300 (standard polystylene equivalent), and polydispersion(Mw/Mn) was 2.19. Note that, the composition ration was determined by¹H-NMR (JNM-GX500, manufactured by JEOL Ltd.), and the molecular weightwas measured by GPC (HLC-8220 GPC, manufactured by Tosoh Corporation).

(1) IR (KBr disk, cm⁻¹): 2912, 1722, 1257, 1155, 1103

Synthesis Example 6) Synthesis of poly(2-methyl-2-adamanthylmethacrylate-γ-butyllacton-3-ylmethacrylate-4-methyl-tetrahydro-2H-thiopyran-4-ylmethacrylate) (Polymerof the Following Formula 7)

To a 100-mL eggplant-shaped flask fitted with a stirrer car coated withTeflon™, were added 1.31 g of 2-methyl-2-adamanthyl methacrylate, 0.57 gof γ-butyllacton-3-yl methacrylate, 0.62 g of4-methyl-tetrahydro-2H-tiopyran-4-yl methacrylate, and 8.2 mL ofdioxane. The mixture was then stirred, and nitrogen gas was bubbled for15 minutes to remove oxygen in the reaction atmosphere. To this, wasadded 0.30 g of AIBN as a radical polymerization initiator, and theflask was placed in an oil bath at 70° C. for 5 hours. The obtainedreaction mixture was cooled to room temperature, and diluted withdioxane to be about 20 mL in volume. The solution was dropped into 500mL of methanol with stirring to give white precipitate. After filteringwith a glass filter, the obtained precipitated resin was dried in vacuoat 50° C. for 6 hours. The resulted resin was dissolved in about 20 mLof THF, was again precipitated in 500 mL of methanol, and filtered anddried in the aforementioned manner to provide poly(2-methyl-2-adamanthylmethacrylate-γ-butyllacton-3-ylmethacrylate-4-methyl-tetrahydro-2H-thiopyran-4-ylmethacrylate) (polymer of the following formula 7). The yield was 1.7 g,the weight average molecular weight was 11,500 (standard polystyleneequivalent), and polydispersion (Mw/Mn) was 1.89. Note that, thecomposition ration was determined by ¹H-NMR (JNM-GX500, manufactured byJEOL Ltd.), and the molecular weight was measured by GPC (HLC-8220 GPC,manufactured by Tosoh Corporation).

IR (KBr disk, cm⁻¹): 2910, 1790, 1720, 1257, 1178

Examples 1 to 3, and Comparative Example 1 Measurement of Absorbance andRefractive Index

A resin solution was prepared using each of the resins of SynthesisExamples 3 to 5 each expressed by Formulae 4 to 6 and the commonlyavailable resin for an ArF resist composition expressed by the followingformula 8. Specifically, 900 parts by mass of propylene glycolmonomethyl ether acetate (PGMEA) was added to 100 parts by mass of eachresin to provide the resin solution. The obtained solution was filteredthrough a 0.2 μm Teflon™ membrane filter to remove particles. Theresulted solution was spin-coated on a silicon wafer, and baked at 110°C. for 60 seconds to form a resin film. The refractive index of eachresin film was measured by a spectral ellipsometer (GES-5, manufacturedby SOPRALAB). In the same manner to the above, the absorbance of eachresin was measured tat 193 nm. The results are presented in Table 1.

TABLE 1 Refractive Transmittance % Resin index Absorbance (filmthickness: solution (400-850 nm) (/μm) 150 nm) Ex. 1 Formula 4 1.5541.48 60.0 Ex. 2 Formula 5 1.524 1.79 53.9 Ex. 3 Formula 6 1.521 0.8275.3 Comp. Ex. Formula 8 1.504 0.20 93.2 1

In Table 1, the transmittance of light is shown with the value that isconverted into that of the film having a thickness of 150 nm. As seenfrom Table 1, all the resins have transmittance of more than 40%, whichis the lower limit for the pattern resolution, and thus these resinshave transparency which is not problem in the practical use. Moreover,the refractive index is the refractive index to the light having awavelength range of 400 nm to 850 nm. It has been known that thematerial having a high refractive index to light having a wavelength of193 nm also has a high refractive index to light having the longerwavelength. As has been described above, when the resin having a sidechain containing thiopyran is used, the refractive index is desirablyincreased while maintaining the transmittance low, compared to theconventional resin for the ArF resist composition (Comparative Example).

Examples 4 and 5 Preparation of Resist Composition

A resist composition for liquid immersion lithography was prepared inthe accordance with the following formulation, using each of thepolymers (resins) expressed by Formulae 6 and 7. As an acid-generatingagent, triphenylsulfonium nonafluorobutane sulfonate (manufactured byMidori Kagaku Co., Ltd.) was used, and as a resist solvent, PGMEA wasused.

Resin 100 parts by mass Acid-generating agent 3 parts by massTri-n-octyl amine 0.02 parts by mass PGMEA 900 parts by mass—Comparison in Resist Performance—

Onto a substrate to which an undercoat antireflection film (BARC,ARC-39, manufactured by Nissan Chemical Industries, Ltd.), the preparedresist composition was spin-coated, and baked at 110° C. for 60 secondsto form a resist film having a thickness of 250 nm. Each resist film wassubjected to ArF liquid immersion lithography, and the sensitivitythereof was compared when the L/S pattern in the size of 200 nm wasformed.

TABLE 2 Resist Sensitivity composition (mJ/cm²) Residual Ex. 4 Formula 640 None Ex. 5 Formula 7 35 None

As seen from above, the resist composition using the resin having a sidechain containing thiopyran has sufficient sensitivity without residualin the exposed area.

Example 6 Production of Semiconductor Device

An interlayer insulating film 12 was formed on a silicon substrate 11 asillustrated in FIG. 1, and a titanium film 13 was formed on theinterlayer insulating film 12 in accordance with a sputtering method asillustrated in FIG. 2. Sequentially, a resist pattern 14 was formed byan ArF liquid immersion exposure as illustrated in FIG. 3, and using theresist pattern 14 as a mask, the titanium film 13 was subjected topatterning by reactive ion etching so as to form an opening 15 a. Thereactive ion etching was continuously preformed so as to remove theresist pattern 14, as well as forming an opening 15 b in the interlayerinsulating film 12 using the titanium film 13 as a mask as illustratedin FIG. 4.

Thereafter, the titanium film 13 was removed by a wet treatment, and aTiN film 16 was formed on the interlayer insulating film 12 inaccordance with a sputtering method as illustrated in FIG. 5 and a Cufilm 17 was sequentially formed on the TiN film 16 in accordance with anelectroplating method. As illustrated in FIG. 6, the surface wassmoothened by CMP while leaving only a barrier metal and the Cu film(first metal film) in a trench corresponding to the opening 15 b (FIG.4) so as to form a wiring 17 a of a first layer.

Thereafter, an interlayer insulating film 18 was formed on the wiring 17a of the first layer as illustrated in FIG. 7, and then, as illustratedin FIG. 8, onto the wiring 17 a of the first layer, a Cu plug (secondmetal film) 19 and a TiN film 16 a which would be connected with awiring of an upper layer formed later were formed in the same manner asillustrated in FIGS. 1 to 6.

By repeating each aforementioned process, a semiconductor device havinga multi-layered wiring structure containing the first layer wiring 17 a,the second layer wiring 20 and the third layer wiring 21 disposed on thesilicon substrate 11 was formed as illustrated in FIG. 9. Note that,barrier metal layers each formed under each wiring were not illustratedin FIG. 9.

In Example 6, the resist pattern 14 was a resist pattern formed by usingthe resist composition of the invention. Moreover, the interlayerinsulating film 12 was formed with a low dielectric constant materialhaving a dielectric constant of 2.7 or less, e.g. a porous silica film(CERAMATE NCS, manufactured by JGC Catalysts and Chemicals Ltd.,dielectric constant: 2.25), or a fluorocarbon film (dielectric constant:2.4) accumulated in accordance with a RFCVD method (power: 400 W) usinga mixed gas of C₄F₈ and C₂H₂ or C₄F₈ gas as a source.

In the examples above, the production methods of the thiopyranderivative, or the polymer containing the monomer unit containing thethiopyran derivative. However, these production methods are described asexamples, and it should be noted that the thiopyran derivative or thepolymer can be also obtained in other conventional methods.

Moreover, the method for manufacturing a semiconductor can be applied tothe productions of those having a fine pattern, e.g., a mask pattern, areticle pattern, functional parts such as metal plugs, various wirings,magnetic heads, liquid crystal displays (LCD), plasma display panels(PDP), and a surface acoustic wave (SAW) filter, optical parts used forconnection of optical wirings, and minute parts such as microactuator.In such productions, the same effects can be attained due to the samefunctions.

Moreover, in the example above, the production process of the flashmemory was specifically explained as an example of the semiconductor,but the example thereof shall not be restricted to the flash memory. Themethod for manufacturing a semiconductor can also provide the sameeffect when it is applied to the production process of a logisticdevice, that of DRAM, or that of FRAM.

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the inventionand the concepts contributed by the inventor to furthering the art, andare to be construed as being without limitation to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification related to a showing of the superiorityand inferiority of the invention. Although the embodiments of thepresent invention have been described in detail, it should be understoodthat the various changes, substitutions, and alterations could be madehereto without departing from the spirit and scope of the invention.

1. A thiopyran derivative, having a structure expressed by the followinggeneral formula 1:

where X is O or S; R₁ is —H, —CH₃, C2-4 alkyl group, thioether group, orketone group; R₂ is —H, —CH₃, or trifluoromethyl group; and R₁ and R₂may be identical to or different from each other.
 2. A polymer,comprising: a monomer unit containing a thiopyran derivative, whereinthe thiopyran derivative has a structure expressed by the followinggeneral formula 1:

where X is O or S; R₁ is —H, —CH₃, C2-4 alkyl group, thioether group, orketone group; R₂ is —H, —CH₃, or trifluoromethyl group; and R₁ and R₂may be identical to or different from each other.
 3. The polymeraccording to claim 2, further comprising a monomer unit containing anacid labile group.
 4. The polymer according to claim 3, wherein the acidlabile group is a 2-alkyladamanthyl group.
 5. The polymer according toclaim 2, further comprising a monomer unit containing a lactonederivative.
 6. The polymer according to claim 2, wherein an amount ofthe monomer unit containing the thiopyran derivative contained in thepolymer is 10 mol % to 55 mol %.
 7. A resist composition, comprising: apolymer comprising a monomer unit containing a thiopyran derivativehaving a structure expressed by the following general formula 1:

where X is O or S; R₁ is —H, —CH₃, C2-4 alkyl group, thioether group, orketone group; R₂ is —H, —CH₃, or trifluoromethyl group; and R₁ and R₂may be identical to or different from each other.
 8. The resistcomposition according to claim 7, wherein the resist composition has arefractive index of 1.520 or more with respect to light having awavelength of 400 nm to 850 nm.
 9. The resist composition according toclaim 7, wherein the polymer is an acrylic resin.
 10. The resistcomposition according to claim 7, further comprising an acid-generatingagent.
 11. The resist composition according to claim 7, furthercomprising a monomer of a thiopyran derivative, wherein the thiopyranderivative has a structure expressed by the following general formula 1:

where X is O or S; R₁ is —H, —CH₃, C2-4 alkyl group, thioether group, orketone group; R₂ is —H, —CH₃, or trifluoromethyl group; and R₁ and R₂may be identical to or different from each other.
 12. The resistcomposition according to claim 7, further comprising a homopolymer of athiopyran derivative, wherein the thiopyran derivative has a structureexpressed by the following general formula 1:

where X is O or S; R₁ is —H, —CH₃, C2-4 alkyl group, thioether group, orketone group; R₂ is —H, —CH₃, or trifluoromethyl group; and R₁ and R₂may be identical to or different from each other.